Electroformation and characterization of Al2O3 embedded nickel matrix composite coatings

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Metalurji ve Malzeme Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2018

Öğrenci: OLGUN YILMAZ

Danışman: İSHAK KARAKAYA

Özet:

The mechanical and tribological properties of electrochemical coatings can be enhanced by embedded second phase particles to nickel matrix. Two different anionic surfactants sodium dodecyl sulfate (SLS) and ammonium lignosulfonate (ALS) were used together to adjust the wetting conditions and provide suspension of Al₂O₃ particles in a nickel sulfamate electrolyte in this study. High performance atomic force microscope (hpAFM), X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscope (SEM) and deposit stress analyzer were used to characterize the composite coatings. The effects of current density and amounts of the two surfactants and alumina particles in the electrolyte on wear rate, coefficient of friction (COF), and hardness were studied. It was found that the amount of incorporated Al₂O₃ dominantly affected the properties of coatings which could be controlled by adjusting the operating parameters. Although combined effects of the surfactants and current density on mechanical and tribological parameters were unpredictable in some cases, the composite coatings possessed superior properties than pure nickel. The presence of alumina particles in the composite coating increased the residual stress. Moreover, it resulted in preferentially oriented and finer nodular grains instead of regular morphology.